1. Field of the Invention
The present invention relates to an antiglare film to be provided on the surface of a window, display etc. In particular, it relates to an antiglare film to be provided on the front surface of display such as a liquid crystal display (LCD), cathode-ray tube (CRT) display, plasma display (PDP), organic electroluminescence display (ELD) and field effect display (FED, SED).
2. Description of the Related Art
It is well known that an antiglare film having concaves and convexes structure (rugged structure) on its surface is provided on a front surface of a display in order to reduce the degradation of visibility due to reflection of external light when viewing a display such as a liquid crystal display, a CRT display, an EL display and a plasma display.
As to an antiglare film, for example, the following technologies are known:    a technology which creates a rugged structure in a surface of an antiglare film by embossing; and    a technology which creates a rugged structure in a surface of an antiglare film by a binder matrix with particles dispersed therein, wherein a coating liquid in which a binder matrix-forming material is mixed with particles is coated.
In an antiglare film whose surface have a rugged structure is obtained by the above mentioned technology, an external light incident on an antiglare film scatters because of the rugged structure, thereby an image obtained by an external light becomes unclear. Therefore, it becomes possible to control degradation of visibility due to reflection of external light in a front surface of a display.
In an antiglare film on the surface of which is formed irregularity through an embossing finish, the surface irregularity thereof can be completely controlled. Consequently, reproducibility is good. However, when there is a defect or an adhered foreign substance on an emboss roll, endless defects occur at the pitch of roll.
On the other hand, the number of processes in the manufacturing of an antiglare film using a binder matrix and particles is smaller than that in the manufacturing of an antiglare film using embossing. Therefore the manufacturing cost of an antiglare film using a binder matrix and particles is lower. Various embodiments of an antiglare film using a binder matrix with particles dispersed therein are known. (Patent Document 1)
As for an antiglare film using a binder matrix and particles, various technologies are disclosed, for example, the following techniques are disclosed.                A technique in which a binder matrix resin, spherical particles and amorphous particles are used in combination (Patent Document 2).        A technique in which a binder matrix resin and plural particles having different particle sizes are used (Patent Document 3).        A technique including surface irregularity, wherein the cross-sectional area of the concave portion is defined (Patent Document 4).        
In addition, the following techniques are disclosed.                A technique wherein internal haze (cloudiness) is 1-15% and surface haze (cloudiness) is 7-30% by using internal scattering and surface scattering in combination. (Patent Document 5)        A technique wherein, while using binder resin and particles having the particle size of 0.5-5 μm, the difference in refraction indices of the resin and the particle is 0.02-0.2 (Patent Document 6).        A technique wherein, while using binder resin and particles having the particle size of 1-5 μm, the difference in refraction indices of the resin and the particle is 0.05-0.15. Further, there are techniques defining a solvent to be used and surface roughness etc. (Patent Document 7).        A technique wherein, using binder resin and plural types of particles, the difference in refraction indices of the resin and the particle is 0.03-0.2 (Patent Document 8).        
The following techniques are also known that reduce the lowering of contrast, hue variation etc. when a viewing angle is altered. In the technique, the surface haze (cloudiness) is 3 or more. Further, the difference between the haze value in the direction of normal line and the haze value in the direction of ±60° is 4 or less (Patent Document 9).
As described above, there are disclosed antiglare films with various constituents for various purposes.
The performance required for an antiglare film differs depending on the displays when it is used on the front face of a display. For example, the optimum antiglare film differs depending on the resolving power of a display, intended purpose etc. A broad range of antiglare films are required according to the intended purposes.
[Patent Document 1] JP-A-6-18706
[Patent Document 2] JP-A-2003-260748
[Patent Document 3] JP-A-2004-004777
[Patent Document 4] JP-A-2003-004903
[Patent Document 5] JP-A-11-305010
[Patent Document 6] JP-A-11-326608
[Patent Document 7] JP-A-2000-338310
[Patent Document 8] JP-A-2000-180611
[Patent Document 9] JP-A-11-160505